Abstract : The requirement for continuous performance for extended periods of time has prompted both laboratory and field studies of the effects of SUSOPS on the performance of a variety of perceptual-motor and cognitive tasks. In the present study we systematically examine the role that practice and task structure play in the moderation of SUSOPS effects in long term memory (LTM), working memory (WM), and visual search processes. Dependent measures include reaction time, accuracy and measures of event-related brain potentials (ERPs). The results suggest that perceptual processes are most susceptible to SUSOPS effects and that proper training may minimize these effects. In recent years there has been a renewed interest in the effects of sustained operations (SUSOPS) on human performance. This interest can be attributed, in a large part, to the requirement for SUSOPS in both military and industrial settings. The requirement for continuous performance, often with little or no sleep, for extended periods of time has prompted both laboratory and field studies of the effects of SUSOPS on the performance of a variety of perceptual-motor and cognitive tasks (Hockey, 1986; Krueger, 1989). In the present study we systematically examine the role that practice and task structure play in the moderation of SUSOPS effects in long term memory (LTM), working memory (WM), and visual search processes.